Final answer:
Calcium and strontium have similar chemical properties because they are both alkaline earth metals, found in Group 2 of the periodic table, and have the same number of valence electrons which dictate their reactivity and the compounds they form.
Step-by-step explanation:
The chemical properties of calcium and strontium are similar because both of these elements belong to the same group in the periodic table. Specifically, they are part of Group 2: The Alkaline Earth Metals, which also includes beryllium, magnesium, barium, and radium. These metals are shiny, good conductors of heat and electricity, and share chemical behaviors due to having the same number of valence electrons, which is two. In chemical reactions, calcium and strontium both readily lose these two valence electrons to form cations with an oxidation state of +2, evident in their similar reactivities and the types of compounds they form.
Additionally, the alkaline earth metals produce alkaline solutions when their oxides react with water, further highlighting their chemical similarities.